The present embodiments relate to calibration for single photon emission computed tomography (SPECT). Sensitivity and/or uniformity of the gamma camera are calibrated.
Calibration is provided for quantitative SPECT imaging. SPECT imaging uses a radiotracer to determine metabolic function within a patient. For example, the uptake of the radiotracer by tissues in the body is measured. Counts of emissions from the radiotracer are detected. The activity concentration of the radiotracer from different locations is reconstructed from the detected emissions. The reconstruction uses the sensitivity and uniformity of the detector. If a class standard sensitivity or uniformity is used, the detector-specific sensitivity or uniformity may be different, contributing a possible source of error in quantitative SPECT imaging.
System-specific sensitivity may be provided using a dose calibrator. The sensitivity of the detector is measured using a source at one energy and an activity of the source measured with the dose calibrator. The dose calibrator may introduce uncertainty, especially where the radioisotope used for the patient scan is at a different energy than the source. Similarly, a sheet source for measuring uniformity corrections may be at a different energy than the radioisotope used for the patient scan. Since the uniformity is emission energy dependent, this difference in energy may introduce uncertainty.